18,19

16

SECTION 31

The urinary system

Fili in the missing verbs in the following text. Choose from the following but you will have to change them into the simple present passive voice.

absorb	alter	cali	eliminate	feel form	lose
pump	recover	reflect	retain	separate	set up
	situate	storę	surround	transport

In the urinary system, waste (1) /s eliminated by the kidneys.

from

A filtrate of water, ion and smali molecules (2) the blood which comes from the renal artery.

The kidney consists of about 1 million units which

(3)_nephrons. Each nephron is a complicated

structure positioned partly in the medulla and partly in the cortex of the kidney.

The glomeruli and proximal convoluted tubules (4)_ in the renal cortex. The glomerulus is a coiled mass of capillaries which

(5)_by specialized cells. Fluid leaves the capillaries

and passes into the lumen of the nephron. The electrolyte composition

of the blood (6)_in the urinary filtrate. Plasma

proteins and blood cells do not pass out but (7)_in

the capillaries.

In the proximal convoluted tubule, sodium ions (8)

from

by the end of

back into the body. Sugars and amino acids (9)_

the filtrate and most of the water (10)_

the proximal convoluted tubule.

Iii 11 i i ' |oii|i <>l Henie, the composition of the filtrate

ill)    _hardly_but a gradient of

iłiilliliii concentration (12)_.

Wriii i ,md lons are further recovered in the distal convoluted tubule.

i nlli i ling ilucts (13)_by several distal convoluted

IiiIhiIi". In Ihe collecting ducts, ions and smali molecules such as urea in rHulncd but water (14)_to the surroundings.

11111 n (15) _in the ureters from each kidney to the

I diii li l«'i wliere it (16)_. When the volume of urine

n a !ii"i between 200 and 300 ml a desire to void urine

(}7) __. Urine is conveyed from the bladder to the

i ^ li i Ii ii vla Ihe urethra.

11 u i pa83lve voice is used to describe processes like those above. It is Inrmod with the verb be and the past participle of the main verb. Regular vi u I >s simply add -d or -ed but you must learn irregular verbs. Luckily, most iiuluntlflc verbs are regular, but there are three irregular verbs above.